Concise Binary Object Representation (CBORRFC 7049) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation.

These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack.

There are hundreds of standardized formats for binary representation of structured data (also known as binary serialization formats). Of those, some are for specific domains of information, while others are generalized for arbitrary data. In the IETF, probably the best-known formats in the latter category are ASN.1's BER and DERASN.1.

The format defined here follows some specific design goals that are not well met by current formats. The underlying data model is an extended version of the JSON data model RFC 4627. It is important to note that this is not a proposal that the grammar in RFC 4627 be extended in general, since doing so would cause a significant backwards incompatibility with already deployed JSON documents. Instead, this document simply defines its own data model that starts from JSON.